Mostly said towards black people. If you are not black and the context isn't a hateful one, this can also be used ironically in a friendly conversation.
man 1: Have you met my sister?
man 2: More than met her, dude.
man 1: Go fuck yourself, nigger.
example 2:
man 1: go play another game you're so bad at this lol
man 2: Go fuck yourself nigger
It means to shove a cactus up your ass or cunt or whatever the fuck you have they're telling you to the nearest cactus and then fuck it
1.Somebody's being extremely obnoxious go fuck yourself with a cactus
2. Someone wants try playing a very cancer game like that stupid cat Pictionary you say how about we play this game it's called go fuck yourself with a cactus the rules are simple go fuck yourself with a cactus
3. Somebody asks you how would you like to do something very stupid
You say how would you like to go fuck yourself of a cactus